function xp = guanacos(t, x)
r=0.001;
a=2.0*(10^(-6));
s=0.01;
b=10^(-6);
xp(1) = r*x(1) - a*x(2)*x(1);
xp(2) = -s*x(2) + b * x(1) * x(2);

xp = xp';